Two station machining vise with removable and off-setting jaws

ABSTRACT

In a wide-opening vise having two movable jaws and a fixed center jaw, the movable jaws are easily removed and reset onto associated slides. The slides have upperly projecting bodies with pressure release latches for positively fixing the jaws in position on the slides. Further, a brake and off-set assembly is associated with one movable slide. The combination allows the second movable jaw, after the first movable jaw has engaged a workpiece, to engage and disengage from a workpiece without effecting the engagement of the first movable jaw with its held workpiece. At least two off-set positions are provided for the engagement and disengagement of the second movable jaw.

This is a Division of application Ser. No. 08/113,048 filed Aug. 31, 1993 now U.S. Pat. No. 5,458,321.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a vise having a stationary jaw and two movable jaws for use in the precision machining of workpieces.

2. Description of Related Art

Two station machining vises are known in the art. U.S. Pat. No. 4,966,350 to Chick discloses a two station device which introduced the concept of a removable stationary jaw bolted to the vise base from above. Thus when it is necessary to machine oversize pieces, the stationary jaw could be removed and one of the movable jaws could be fixed in position.

Another two station vise is disclosed in U.S. Pat. No. 4,529,183 to Krason et al. The vise consists of a stationary center jaw and two movable jaws. One movable jaw is fixed positionally on the screw shaft 2 which threadably engages the slide of the second movable jaw. The shaft itself is capable of axial movement within the vise base so as to enable grasping workpieces of different sizes.

U.S. Pat. No. 4,529,183 also discloses mounting removable jaw blocks over upward extensions of the slides. Between a front surface of the slide projection and the inner surface of the cavity of the jaw block is a hemispherical segment for engaging with the surface of the protrusion. The opposite side of the upper protrusion is engaged by a set screw 60 to lock the jaw block onto the slide. Similar constructions for the mounting of jaw blocks are found in U.S. Pat. Nos. 4,098,500 and 4,685,663.

Another method of mounting a jaw block to a slide is disclosed in U.S. Pat. No. 5,024,427 to Swann. As disclosed, the upward extension from the slide has a detent pin on one of the upwardly extending vertical faces and a hemispherical opening passing through the extension transverse to the orientation of the detent pin. The jaw block has an opening aligned with the hemispherical opening. A pin, with a handle, is inserted into the opening in the jaw and passes through the hemispherical opening in the slide extension to engage the jaw block to the slide.

Off-set devices or staggered release mechanisms have also been provided in two-station machining vises. One such vise is disclosed in U.S. Pat. No. 4,934,674 to Bernstein. This vise employs a drive shaft having counter threads at opposing ends for engaging the respective movable jaw slides. An assembly at one end of the vise screw allows the movable jaws to be positioned with respect to the stationary jaw and locked into position. Such a mechanism permits a first workpiece to be subjected to a preclamping load before the second workpiece is clamped by the second movable jaw. In this apparatus each time a size difference occurs between the workpieces being positioned at the two workstations, the apparatus must be adjusted by releasing a set screw from the screw shaft and repositioning the screw shaft.

U.S. Pat. No. 5,022,636 to Swann also discloses a locking, staggered release apparatus. In this apparatus, a biasing means is fixed by means of a set screw to the vise base. The biasing means is spring attached to a one of the slides. By properly positioning the biasing means, the slide that is not attached to the biasing means will first engage, through its jaw block, the workpiece at the first workstation and then the second slide attached to the biasing means will engage, by means of its jaw block, the second workpiece at the second workstation. Each time differently sized workpieces are to be machined, the set screw must be released and the position of the biasing means adjusted.

U.S. Pat. No. 5,098,073 to Lenz discloses another method of providing for staggered release of the movable jaws. The apparatus includes a holding block that may be positioned on a sleeve to shift the vise screw assembly thereby repositioning the movable jaws relative to the center block. The holding block is a split collar type block that can be loosened so that the sleeve can be slid axially relative to the holding block.

SUMMARY OF THE INVENTION

The invention relates to two-station vise that can hold two workpieces to be machined against oppositely facing surfaces of a stationary jaw mounted to a center of the vise body. The movable jaws move toward and away opposite surfaces of the stationary center jaw for clamping the workpieces therebetween. A threaded screw is rotatably mounted in one movable jaw slide and threadably engages a bore of the second movable jaw slide. The slide of one movable jaw has a hood covered recess and the slide of the other movable jaw has an extension so that the extension may enter the recess to increase the jaw travel and permit the movable jaws to contact the stationary jaw. A break and off-set assembly are resiliently attached to the second slide to permit non-simultaneous engagement of workpieces at the two work stations.

It is an object of the invention to use the threaded screw with a brake applied to one jaw slide to position the movable jaws for non-symmetrical workstations.

It is another object of the invention to permit the movable jaws to be positively mounted to the respective slides but to be quickly releasable and replaceable.

It is still another object of the invention to permit the maximum jaw travel while maintaining positively seated jaws on the movable slides.

It is a further object of the invention to provide a plurality of off-set positions such that pre-release of one movable jaw prior to the release of the second movable jaw permits the handling of workpieces having varying configurations and degrees of tolerance with a minimum of cranking and uncranking to release the workpieces. Further, when used with parallels, the ledge is maintained to support the workpiece when the workpiece is initially released.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the drawings in which:

FIG. 1 is a side view of the invention partially cut away and partially in cross-section;

FIG. 2 is a plan view of the invention;

FIGS. 3A and 3B are a divided cross-section of the invention in the fully opened position, the division occurring at the center of the stationary jaw;

FIG. 4 is an angled view of the jaw retainer;

FIG. 5A is a cross-section of the jaw retainer;

FIG. 5B is a plan view of a jaw block;

FIG. 5C is a cross-section of an alternate embodiment of a jaw block mounted on a jaw retainer;

FIG. 6 is a cross-section of the off-set mechanism and brake as indicated by 6--6 in FIG. 3A;

FIG. 7 is a cross-section of the off-set mechanism as indicated by 7--7 in FIG. 3A;

FIG. 8 is a cross-section of the off-set mechanism as indicated by 8--8 in FIG. 3A;

FIG. 9 is an exploded view of an off-set;

FIG. 10A is a plan view of the detent as indicated by 10--10 in FIG. 9;

FIG. 10B is an interior view of an end cap as indicated by 10--10 in FIG. 9; and

FIG. 11 is an exploded view of the off-set with attachment assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A two-station machine vise, shown in FIGS. 1 and 2, and indicated generally at 20 has a vise body 23 with an elongated longitudinal central axis and a base 35. Although not shown, the outer surface for the base 35 may have projections or ears for mounting the body 23 to a work surface or may have other mounting features for mounting the vise to various machines used for machining operations. The sides 32 extend from the base 35 and have in-turned upper rails 30. The rails 30 define a channel 38 therebetween. A second, and larger, channel 39 (FIG. 7) is formed below the rails 30. A contact surface 36 (FIG. 6) extends longitudinally along the bottom of the second channel 39.

At a center position of the body 23, transverse to the longitudinal axis, is a groove 31 that is cut into rails 30. A jaw block 60 of a stationary jaw 26 is removably mounted on and transverse to the rails 30 (FIGS. 1 and 2). An extension 64 of the jaw block 60 engages the groove 31. Further, the bolts 62 extend through bores in the jaw block 60 and are threadably received in bores in the rails 30 to fix the stationary jaw 26 in position. Not shown, are jaw plates that may be bolted to block faces 65 of the jaw block 60.

Opposing the stationary jaw 26 are movable jaws 24, 25. The movable jaws 24,25 have a jaw block 40 mounted on body 101 (FIG. 5A) of the respective male and female slides 27,28. The jaw blocks 40, as can the jaw block 60, can be either soft or hard jaw blocks. When hard blocks are used, a jaw plate 41 is attached to the jaw block 40 by means of bolts 42. Additionally, jaw parallels, (not shown), such as those described in U.S. Pat. Nos. 4,923,186 and 5,037,075, the disclosures of which are incorporated by reference, may be used with the jaw plates 41 and those mounted to the jaw block 60 of the stationary jaw 26.

At the bottom of the jaw block 40 is a guide extension 45 that fits into the channel 38. The bottom surface of the guide extension 45 rests upon the top surface of the respective slide 27,28 and shoulders to either side of the guide extension 45 substantially rest on the upper surface of the rails 30.

To mount the jaw block 40 onto a slide 27,28, a recess 44 (FIGS. 5A-5C) extends into the under surface of the block 40. The recess 44 receives the body 101, of a jaw block retainer 100, to be discussed below, of the respective slide 27,28. In an end of the recess 44, away from the face of the jaw block 40 is a notch 48. A rod 46 inserted through a bore 53 in the jaw block 40 and having a planar surface is partially exposed at a forward end of the recess 44 closest to the jaw face of the jaw block 40. The planar surface is capable of limited rotation to allow the flat surface to adapt to a surface of the body 101 as described below. The length of the rod 46 is slightly greater than the width of the recess 44. The rod 46 is retained in jaw block 40 by means of either a pin 55 inserted through a slot in an end of the rod 46, the diameter of the pin 55 being less than the width of the slot, or by the pin 55 engaging a groove at one end of the rod 46 (not shown).

When soft jaws are used, the structure of the jaw block 40 provides a maximum area for machining of the upper surface of the jaw block 40 to accommodate workpieces having irregular shapes. Further, an alternative embodiment for a soft jaw block 40a is shown in FIG. 5C wherein each end of recess 44 has a notch 48 and a rod 46. This construction of the soft jaw block 40a permits the soft jaw to be machined at either end to provide a jaw face for different irregularly shaped workpieces. By permitting machining at both ends, economies are achieved.

A jaw block 40 is mounted to the body 101 of the jaw block retainer 100 of each of the respective male and female slides 27,28. The body 101 extends upwardly from the slide 27,28 through channel 38 between rails 30 (FIG. 5A). The body 101 has mounted, at a side away from the jaw face, a release mechanism therein. The release mechanism comprises a latch 105 and a spring 103 that are mounted in a bore in the body 101. Latch 105 is retained in the body 101 by means of a retainer screw 109. A forward end of the body 101, that is the end toward the face of the block 40, has an extension 110 with a sloped under surface 111. Under surface 111 is a part of a substantially V-shaped recess in the body 101 for accommodating rod 46.

The contact of the planar surface of the rod 46 is adapted to the surface of the body 101 and provides an angle lock that adds stability to the jaw block 40. When pressure is applied to the face of the jaw block 40, the planar surface of the rod 46 rides down the under surface of 111 of the body 101 to press the jaw block 40 against an upper surface of the slide 27,28. Rod 46 does not contact the lower surface of recess 108.

To mount jaw block 40 to body 101 the forward part of recess 44 is placed over body 101. The planar surface of the rod 46 engages the sloped under surface 111 of the extension 110. The rear portion, that is the portion away from the jaw face, is then pushed down so that the latch tip 107 of the latch 105 engages the notch 48 to lock the block 40 onto the body 101. The jaw block 40 is removed by inserting a rod in the bore 50 and applying a force to the upper end of the rod. The force is applied in the direction of the stationary jaw 26 causing the rearward portion of the jaw block 40 to be unseated from the latch tip 107 of the latch 105 for easy removal of the jaw block 40.

The male slide 27 and the female slide 28 are moved by means of a threaded screw 29 (FIGS. I and 2). The threaded screw 29 passes through a through bore 83 and is received in a receiving bore 82 of the female slide 28. A seating head 90, at one end of the threaded screw 29, is seated against a thrust bearing 92 and a second thrust bearing 92 is placed on the other side of the seating head 90. The entire assembly is retained within the female slide 28 by a retention plate 88 which is mounted to the female slide 28 by means of bolts 89. The retention plate 88 is seated in a recess 84 in the end surface of the female slide 28.

A handle engager 94, shown in FIGS. 1 and 3B as a recess, can also be a projection. In the preferred embodiment, handle engager 94 is a polygonal shaped recess for receiving a complementary shaped rod having a handle at the opposite end of the rod. The rod is of sufficient length such that when the female slide 28, mounted in one end of the body 23, moves to bring the jaw plate 41 into contact with the stationary jaw 26, the handle may still be freely rotated without contacting the body 23.

The female slide 28 has a hood 75 spaced apart from but extending around threaded screw 29. The hood 75 provides increased strength to the female slide 28 as the upper surface of the hood 75 contacts the under surface 33 of the rails 30. Mounted at the opposite end of the base 23, in second channel 39, is the male slide 27. At an end toward the female slide 28, the male slide 27 has a bore extension 72 having an internally threaded bore 70 that extends through the male slide 27. The threaded screw 29 threadably engages the threaded bore 70. As the movable jaws 24,25 mounted to the male slide 27 and the female slide 28 respectively are moved toward engagement with stationary jaw 26, the bore extension 72 enters into the gap between the hood 75 and the threaded screw 29. This structure provides added travel and permits the movable jaws 24,25 to be brought into contact with the stationary jaw 26.

At the other end of the male slide 27 from the bore extension 72, it is a seat 164 with an off-set extension 77 (FIGS. 9 and 11). Mounted to the off-set extension 77 is an off-set mechanism which, in combination with the off-set extension 77, provides an off-set assembly. The off-set mechanism comprises an off-set body 140, a detent 141, a detent spring 142, and an end cap 143.

The off-set body 140 is received on the seat 164 of the male slide 27. The off-set extension 77 extends into a bore 161 of the off-set body 140. The off-set body 140 is maintained in position by a pair of bolts 73 passing through bolt bores 71 on either side of the male slide 27. Limit bores 162, having internal threads, receive the threaded bolts 73. Between each bolt head 79 and an end of an enlarged bore for receiving the bolt head 79 is a spring 76. The springs 76, in combination with the bolt heads 79, cause a recess 163 of the off-set body 140 to be drawn onto and seated on the seat 164 of the male slide 27.

Three pairs of notches 78 (FIGS. 7 and 9) are placed in the end of the off-set extension 77. The notches 78 of each pair are off-set from one another by 180°. One pair of notches 78 defines an axis perpendicular to the longitudinal axis of the body 23, the axis of this base pair of notches 78 passing through a midpoint of the channel 38 and the contact surface 36. A pair of the remaining two pairs of notches 78 are off-set at an angle of 45° to either side of the base pair of notches 78.

The end cap 143 has a spring seat 153 extending from its base into its interior and extending from the inner periphery of the end cap 143 are off-set protrusions 150. In the center of the spring seat is an adjustment receptacle 155 for receiving an adjustment tool. The detent spring 142 is seated around spring seat 153. The detent 141 is placed over the detent spring 142, which is received in a spring counter bore 146 of the detent 141, so that detent arms 145 are seated in detent seats 151 of the end cap 143. The opposite sides of the detent arms 145 also engage a pair of notches 78 in order to set the off-set. The end cap 143 with the detent spring 142 and the detent 141 is inserted into the off-set body 140 so that off-set protrusions 150 are received in notches 144 of the off-set extension 77. The off-set extension 77 is seated in an off-set extension counter bore 159 of the end cap 143.

The end cap 143 is received in an end cap bore 165 of the off-set body 140. At the base of end cap bore 165 are a lip and two pairs of recesses. The lip and recesses form off-set sinks 169 which are engaged by the off-set protrusions 150. Each recess of a pair of recesses is off-set from the other by 180° and there is a separation of between pairs of recesses of 45° from a center line of each pair. The depth of the off-set sinks 169 determines the amount of off-set available.

When the end cap 143 is assembled to off-set body 140, the off-set projections 150 are aligned with notches 144. This permits ribs 152 of off-set projections 150 to pass over the end of the off-set extension 77. The end cap is then rotated clockwise at least 45° and preferably 90° to engage the ribs 152 in grooves 154 thereby attaching the end cap 143 to the off-set extension 77. With this rotation, the detent arms 145 are engaged with a base pair of notches 78 to establish a base off-set. Rotating the end cap 143 a predetermined number of degrees in either direction then sets the alternate off-sets. In the preferred embodiment, using three off-sets, the predetermined number of degrees is 45°. The rotation to engage the ribs 152 in the grooves 154 must be greater than the predetermined number of degrees to prevent an inadvertent disengagement of end cap 143 from the off-set extension 77. After the end cap 143 is engaged with the off-set extension 77, the off-set body 140 is positively attached to the male slide 27 using the bolts 73.

When the end cap 143 is inserted into the off-set body 140, a retention groove 157 opposes a socket head cap screw 167 threadably received in a threaded hole and counter bore in the off-set body 140. The socket head cap screw 167 extends into the retention groove 157 of the end cap 143. Alternatively, a set screw or other retention structure, such as a detent pin that is received in the retention groove 57 for retaining the end cap 143 in the off-set body 140 while permitting it to rotate, are possible.

A brake assembly 120 (FIG. 6) is provided in the off-set body 140. The brake assembly 120 comprises a U-shaped brake 122 that is pivotally mounted, by means of a pin 126, in the off-set body 140. The brake 122 is transverse to the longitudinal axis of the body 23. A contact surface 124 is provided on the lower surface of the brake 122 to engage the contact surface 36 of the body 23. The contact surface 124 may be metal, as is the case with the brake 122, or may be a brake material adhered to the brake 122.

At the upper ends of the arms of the U-shaped brake are surfaces 130,131. Surface 130, which is adjacent the pivotal mounting located in one of the arms of the brake 122, contacts a spring 128 received in a recess in the off-set body 140. The spring 128 applies a pressure to the surface 130 to cause the brake 122 to pivot around the pin 126 and become recessed in the off-set body 140. A bolt 132, passing through a threaded bore in the off-set body 140, contacts the upper surface 131 of the second arm of the U-shaped brake 122. Adjustment of the bolt 132 causes the contact surface 124 of the brake 122 to engage the contact surface 36 of the body 23. When bolt 132 bottoms out, it loads spring pressure on the U-shaped brake 122 creating the tolerance necessary to promote even wear on the contact surface 124.

The dual-station vise having the structure described above may be operated to open and close the movable vise jaws such that a workpiece at one station is engaged first followed by the engagement of a workpiece at a second workstation. During release of the workpieces by backing off the movable jaws, the workpiece at the second workstation is released first and then the workpiece at the first workstation is released.

To prepare the vise for operation, a handle, not shown, is attached to the handle engager 94 and rotated to move the movable jaws 24,25 to their open most position. Because the brake 122 is engaged, the movable jaw 24 attached to the male slide 27, does not move initially and the movable jaw 25, attached to the female slide 28, is opened until it encounters a stop (not shown) at the end of the body 23. Because the female slide 28 can move no further, continued rotation of threaded screw 29, by the rotation of the handle, causes the movable jaw 24, mounted to the male slide 27, to be moved in the opening direction overcoming the resistance of the brake 122.

To remove the movable jaw 24 for maintenance, the jaw block 40 of the movable jaw 24 can be removed from the male slide 27 allowing access to the bolt 132. By backing off the bolt 132, the spring 128 forces the brake 122 to disengage from the contact surface 36.

Prior to closing the movable jaws 24,25, to engage the workpieces, the brake 122, if released, must be reset by tightening the bolt 132 to ensure that the contact surface 124 of the brake 122 engages the contact surface 36 of the body 23. Additionally, the operator must set the desired off-set.

The off-set is established by inserting a wrench into adjustment receptacle 155 and rotating end cap 143. The rotation of end cap 143 positions detent arms 145 in one of the pairs of notches 78 in the off-set extension 77, each pair of notches 78 corresponding to an off-set dimension. Simultaneously, the off-set protrusions 150 are aligned with the corresponding pair of off-set sinks 169 to establish the amount of off-set.

In the preferred embodiment, the possible off-sets are 1/8, 1/16 and 1/32 inch. However, the invention is not limited to three off-sets nor is it limited to the preferred depths as depths of 1/16, 1/8 and 1/4 inch may also be appropriate.

At this time, the operator insures that the desired jaws, be they hard or soft jaws, necessary parallels, or other accessories, are mounted to the vise. Holding a first workpiece for clamping at a first workstation between the stationary jaw 26 and the movable jaw 25, mounted to the female slide 28, the handle is rotated and the female slide 28 is moved toward the stationary jaw 26 to engage the workpiece between the movable jaw 25 and the stationary jaw 26. When the first workpiece is engaged, male slide 27 commences movement overcoming the braking force provided by the brake 122. In so doing however, the off-set body 140 is initially held in position while the male slide 27 commences closure. As a result the springs 76 are compressed by the heads of bolts 79 as the male slide 27 separates the off-set distance from off-set body 140. The amount of separation permitted is controlled by the off-set set by the rotation of end cap 143. Because the end cap 143 is engaged with the offset extension 77 by the engagement of the ribs 152 in the grooves 154, the movement of the male slide 27 causes movement of end cap 143 resulting in the off-set protrusions 150 contacting or engaging the selected pair of off-set sinks 169.

Further, as the male slide 27 pulls away from off-set body 140 prior to overcoming the resistance of brake 22, an opening in detent 141 allows spring seat 153 to pass therethrough.

When the end cap 143 has engaged the off-set sinks 169 of the off-set body 140, the off-set body 140 is caused to move in the closing direction. When the second workpiece is engaged and clamped between the movable jaw 24 and the stationary jaw 26, the off-set body 140 is held in position by the brake assembly 120. Thus, when action is taken to open the jaws, the male slide 27, as a result of the expansion of the springs 76, is caused to open first by the off-set amount. Thus, the second workpiece may be removed. Further rotation of the handle causes the female slide 28 to move as the male slide 27 is held in position by the brake assembly 120. As a result, the first workpiece is released.

Although the action has been described as requiring both movable jaws to be moved to the fully open position, it is necessary only to move the movable jaw 25, attached to female slide 28, to the stop position which in turn forces movement of the male slide against the resistance of the brake 122 to open a distance sufficient to allow insertion of the second workpiece and establish the desired off-set.

Although the invention has been described with great particularity, the invention is not limited to the description as other variations, such as the number of off-sets, reversing the mounting of the threaded screw and the off-set assembly with respect to the male and female slides, manner of creating the off-sets and manner of fixing the end cap to the slide are possible. Further, the snap-lock concept for mounting the jaw block to the movable slides is applicable to a single station vises or multi-station vises. 

What is claimed is:
 1. A method of operating a vise comprising a stationary jaw mounted between first and second movable jaws that reciprocate relative to the stationary jaw through rotation of a vise screw, the second movable jaw being attached to an off-set mechanism, the method comprising the steps of:applying a brake in the off-set mechanism to create a frictional resistance in the off-set mechanism to resist movement of the second movable jaw upon rotation of the vise screw in a first direction but to allow movement of the first movable jaw; impeding movement of the first movable jaw while continuing rotation of the vise screw; and overcoming the frictional resistance of the off-set mechanism to allow movement of the second movable jaw and the off-set mechanism while the brake is applied.
 2. The method of claim 1, wherein the step of impeding movement of the first movable jaw includes clamping a first workpiece between the stationary jaw and the first movable jaw.
 3. The method of claim 1, wherein the step of overcoming the frictional resistance of the off-set mechanism includes the steps of first moving the second movable jaw relative to the off-set mechanism by a predetermined off-set amount after movement of the first movable jaw is impeded and then moving the off-set assembly and second movable jaw by continued rotation of the vise screw.
 4. The method of claim 1, wherein the step of overcoming the frictional resistance of the off-set mechanism includes the sequential steps of:urging the second movable jaw toward the off-set mechanism to unclamp a second workpiece between the stationary jaw and the second movable jaw, the second movable jaw moving away from the workpiece by at least one predetermined off-set amount; moving the first movable jaw away from the stationary jaw to unclamp a first workpiece between the stationary jaw and the first movable jaw; and stopping movement of the first movable jaw at an end of the vise while continuing rotation of vise screw to move both the off-set mechanism and the second movable jaw while the brake is engaged.
 5. A method of operating a vise comprising a stationary jaw mounted between first and second movable jaws that reciprocate relative to the stationary jaw through rotation of a vise screw, the second movable jaw being attached to an off-set mechanism, the method comprising the steps of:applying a brake in the off-set mechanism to create a frictional resistance in the off-set mechanism to resist movement of the second movable jaw upon rotation of the vise screw in a first direction but to allow movement of the first movable jaw; moving the first movable jaw toward the stationary jaw to clamp a first workpiece therebetween; moving the second movable jaw away from the off-set mechanism by at least one predetermined off-set amount, the off-set mechanism being held stationary by the brake; overcoming the frictional resistance of the brake after the second movable jaw has moved the predetermined off-set amount by continued rotation of the vise screw in the first direction and the first movable jaw has clamped the first workpiece to move both the off-set mechanism and the second movable jaw toward the stationary jaw to clamp a second workpiece between the stationary jaw and the second movable jaw; rotating the vise screw in a second opposite direction; urging the second movable jaw toward the off-set mechanism as the vise screw rotates in the second direction to move the second movable jaw away from the second workpiece by the predetermined off-set amount to unclamp the second workpiece, the off-set mechanism being held stationary by the brake; and resisting movement of the second movable jaw and off-set mechanism with the brake as the vise screw continues to rotate in the second direction, thereby moving the first movable jaw away from the stationary jaw to unclamp the first workpiece.
 6. The method of claim 5, further comprising the steps of:stopping the movement of the first movable jaw after the first workpiece is unclamped at an end of the vise; and overcoming the frictional resistance of the brake by continued rotation of the vise screw in the second direction to move both the off-set mechanism and the second movable jaw away from the stationary jaw.
 7. A method of setting an off-set in a two-position vise, comprising the steps of:rotating a vise screw in a first direction to clamp a first workpiece between a jaw on a first movable slide and a first jaw face of a stationary center jaw; then separating a jaw on a second movable slide from an off-set assembly mounted to the second movable jaw by an off-set amount by continued rotation of the vise screw in the first direction; then overcoming resistance of a friction brake of the off-set assembly by the continued rotation of the vise screw in the first direction; closing the jaw on the second movable slide by the rotation of the vise screw toward a second jaw face of the stationary center jaw; and clamping a second workpiece between the second jaw face and the jaw on the second movable slide, wherein the second movable slide is separated from the off-set assembly by the off-set amount when the second workpiece is clamped.
 8. The method of claim 7, further comprising the steps of:selecting an appropriate off-set; and adjusting an off-set mechanism in the off-set assembly to the selected off-set.
 9. The method of claim 8, further comprising the steps of:changing the off-set, when a third workpiece is to be clamped in place of the second workpiece and the third workpiece is smaller than or requires smaller tolerances than the second workpiece, by turning the vise screw in a second direction to move the second slide member into contact with the off-set assembly; adjusting the off-set mechanism to the newly selected off-set; and turning the vise screw in the first direction to clamp the third workpiece by the movement of the second slide member and the off-set assembly, separated by the off-set amount, toward the stationary center jaw. 